The Orphan Tsunami

March 15, 2011 2:01 PM

Around midnight on January 27, 1700, a mysterious tsunami stole through several villages on the eastern coast of Japan.

But in the days leading up to the 1700 tsunami, no earthquakes had been detected. Miho's leader wrote that such a thing was unheard of and wondered what to call the waves. "It is said that when an earthquake happens, something like large swells result, but there was no earthquake in either the village or nearby," he wrote. With no parent earthquake to claim it, the tsunami was labeled an "orphan."

Based on geologic evidence, scientists think that a massive magnitude-9.0 earthquake rocked the Cascadia Subduction Zone region off Oregon and Washington sometime between 1680 and 1720. In 1997, analysis of tree-rings from the Cascadia region narrowed the time of the natural disaster to a 10-month window, from August 1699 to May 1700.

In Japan this event triggered the Orphan Tsunami.

(The last link is to a 144 pg. pdf document that will take forever to load, will tie up your computer while it does, but to the geology or history nerd, so worth it.)

posted by Danf (18 comments total)

Temblor [tem-bler, -blawr; Sp. tem-blawr] n. A word meaning "earthquake" used exclusively when journalists run out of other synonyms
posted by Riptor at 2:07 PM on March 15, 2011 [7 favorites]

What me Worry?
posted by TwelveTwo at 2:09 PM on March 15, 2011

Oh man, this is fantastic. I've read accounts of the 1700 tsunami and those villages, and they always left me with this icy sense of dread. That we can, this long after the fact, find what caused that wave, makes me think, for a moment, humans are awesome and not totally screw ups after all.
posted by strixus at 2:10 PM on March 15, 2011 [3 favorites]

The same earthquake may have been the cause of the Bonneville Slide and the Bridge of the Gods in the Columbia River Gorge.
posted by Mister Fabulous at 2:10 PM on March 15, 2011

Japan has had catastrophic earthquakes every 70 years according to an article I read by Michael Lewis (of Liars Poker) called How a Tokyo Earthquake could Devastate Wall Street and the World Economy...highly recommended if you want an 89 take on the interconnection of markets, not the nuclear angle...
posted by lslelel at 2:14 PM on March 15, 2011 [3 favorites]

Cool post. I self linked to a post from my blog in the Japan earthquake thread, but here it is again since it is more relevant to this thread - Oregon oral history and geology reveal long-term tsunami threats.
posted by Rumple at 3:12 PM on March 15, 2011 [2 favorites]

Just skimming that pdf has totally fascinated me. I have literally thousands of pages of work that I should read through, but this just found its way to the top of the list. Great find!
posted by Guernsey Halleck at 3:33 PM on March 15, 2011

Although geologist Brian Atwater has done most of the seminal writing about the Cascadia Subduction Zone earthquake of 1700, a particularly accessible piece of writing about that quake is this one.

Atwater did participate in this piece: Surviving a Tsunami—Lessons from Chile, Hawaii, and Japan
posted by bz at 3:39 PM on March 15, 2011 [1 favorite]

I found it really surprising how unprepared people were for the Nisqually earthquake in 2001, having grown up in southern California where earthquake drills were just a way of life. Then thinking that Cascadia could experience a 9+ magnitude quake...boggles the mind.
posted by epersonae at 5:32 PM on March 15, 2011

Thank you for this. I have been aware of the 1700 earthquake for some time now, but not to the extent that the various links provide. I live in Vancouver BC, and it's funny, because even though there will be a huge earthquake close enough to do lots of damage at some near point in the future, it never seems to quite register except when something like Japan happens. It's as though if we can avoid thinking about it, somehow it won't happen.
posted by Phlegmco(tm) at 6:04 PM on March 15, 2011

That we can, this long after the fact, find what caused that wave, makes me think, for a moment, humans are awesome and not totally screw ups after all.

The geological record reveals that "great earthquakes" (those with moment magnitude 8 or higher) occur in the Cascadia subduction zone about every 500 years on average, often accompanied by tsunamis. There is evidence of at least 13 events at intervals from about 300 to 900 years with an average of 590 years. Previous earthquakes are estimated to have occurred in 1310 AD, 810 AD, 400 AD, 170 BC and 600 BC.

As seen in the 1700 quake and the 2004 Indian Ocean Earthquake, subduction zone earthquakes can cause large tsunamis, and many coastal areas in the region have prepared tsunami evacuation plans in anticipation of a possible future Cascadia earthquake. However, the major nearby cities, notably Seattle, Portland, Vancouver, Victoria, and Tacoma, which are located on inland waterways rather than on the coast, would be sheltered from the full brunt of a tsunami. These cities do have many vulnerable structures, especially bridges and unreinforced brick buildings; consequently, most of the damage to the cities would probably be from the earthquake itself. One expert asserts that buildings in Seattle are vastly inadequate even to withstand an earthquake of the size of San Francisco 1906, much less the much greater one that may well occur.

posted by DU at 6:39 PM on March 15, 2011 [3 favorites]

Thanks for posting this. I read the book a couple of years ago and had been meaning to make a post about it. I will be spending an upcoming weekend in Seaside and I will park my car facing east.
posted by neuron at 6:40 PM on March 15, 2011

Seismic Vulnerability of Oregon Highway Bridges (pdf). In a nutshell: when the Cascadia Subduction Zone earthquake happens, 70 bridges in western Oregon are going down.
posted by neuron at 6:46 PM on March 15, 2011 [1 favorite]

Meef in the Seattle-Vancouver area might be interested in the Canadian DFO page on tsunamis, including the animated tsunami threat model for the Salish Sea and open coasts of southern BC and Washington - let the model load its 700+ frames and it will run smoothly - or as smoothly as javascript on a mac ever does!

There is a higher resolution model here, but even the lower resolution one shows some alarming features such as the big red dot which forms on Bellingham Bay.

There are also higher resolution detailed models for Esquimalt Harbour and Victoria Harbour.

Incidentally, while a Cascadia megathrust earthquake is likely to create a tsunami coming in from the offshore, there is an equal or greater risk that a smaller quake - even quite a small one indeed - could collapse part of the underwater fore-set bulge of the Fraser River delta, which could create a landslide-generated tsunami within the Salish Sea of substantial proportions.
posted by Rumple at 7:16 PM on March 15, 2011 [1 favorite]

Around midnight on January 27, 1700, a mysterious tsunami stole through several villages

Was it a ninja-tsunami, sneaking through the villages without being noticed?
posted by CaseyB at 7:54 PM on March 15, 2011

Hey it's almost Tsunami Awareness Week!

And I get to link to tree ring information that is also relevant. I thought this was pretty cool.
posted by Xoebe at 7:58 PM on March 15, 2011

Yeah Cascadia! BOOOOO tsunamis and earthquakes!
posted by rainperimeter at 10:43 PM on March 15, 2011

One expert asserts that buildings in Seattle are vastly inadequate even to withstand an earthquake of the size of San Francisco 1906, much less the much greater one that may well occur.

That we pretend these sorts of events don't happen to this point scares the crap out of me. I remember living through an earthquake here in Atlanta. And yet, most people I talk to, even those living here when it happened, have no idea it even could happen here.

I know the building I live in now, and the one I work in every day, would both fall like matchsticks in anything of reasonable power. I suppose my comfort would be dying quickly in that pile of rubble.
posted by strixus at 10:55 PM on March 15, 2011